By no means is it purely subjective, I use ALL of the above criteria you list and then some - (6 categories in total vs. your 4) in my personal scoring criteria @limabeing. So does @krystle, and so does @meno... All of us employ each of those categories and MORE!
However, there is simply no getting around some level of "subjectivity" even amidst the tightest of constraints scoring entrants amid very specific categories.
What you consider "a good performance" I may consider "fantastic."
What one may consider being simply "good" use of theme, melody, or lyrics, another may consider such "phenomenal."
I trust you get the honest and realistic nature of what judging is all about.
The performers and artists are not lifeless robots void of feelings and emotion - and nor are the judges. We're all simply human.
I trust that much you can agree with and understand.
At the end of the day, this is NOT the Olympics but rather a friendly competition amongst supportive artists seeking to challenge themselves and each other to better their crafts, develop friendships and collaborations, and most importantly, to have fun and to experience the joy that music brings to each and every one of us.
PS.
It would be overly cumbersome to track each and every entrant's point's (though I personally considered it) Ha!
After a great deal of realistic discussion, we've decided to only track those entrants who place within any given Top-5 list.
That's not to say, however, that there won't be incentives and realistic opportunities for someone to come from behind - or out of nowhere and begin "placing" - especially in the latter half of the contest... :-)
You articulate that really well @passion-ground.
To @limabeing (great handle, by the way) I understand your curiosity.
We want you to focus on writing, performing, and building connections with the community here. Let us worry about the judging details. Have fun.